Add support for creating Python interpreters

2 files changed, 60 insertions, 19 deletions

diff --git a/python/engine.py b/python/engine.py
index 4a12443..51c08b4 100755
--- a/python/engine.py
+++ b/python/engine.py
@@ -1,30 +1,63 @@
 #!/usr/bin/python3
 
-# This module submits Python code to the python-tester.
-
+from fcntl import fcntl, F_GETFL, F_SETFL
 import http.client
 import json
+import os
+import subprocess
 
-address, port = 'localhost', 3031  # TODO put this somewhere sane
-def request(path, args=None):
-    headers = {'Content-Type': 'application/json;charset=utf-8'}
-    body = json.dumps(args)
-    try:
-        conn = http.client.HTTPConnection(address, port, timeout=30)
-        conn.request('GET', path, body=body, headers=headers)
-        response = conn.getresponse()
-        if response.status != http.client.OK:
-            raise Exception('server returned {}'.format(response.status))
-        reply = json.loads(response.read().decode('utf-8'))
-        return reply
-    finally:
-        conn.close()
-
-# Inputs are given as a list of pairs (expression, stdin). Receives and returns
-# a list of answers given as tuples (result, stdout, stderr, exception).
+# For each input, load [code] into a new environment and run it using a Python
+# runner daemon (so we can get structured results instead of parsing stdout).
+# Inputs are given as a list of pairs (expression, stdin). Return a list of
+# answers as tuples (result, stdout, stderr, exception). If the code times out
+# on some input, 'timed out' is returned instead at the corresponding position
+# in the answer list.
 def run(code=None, inputs=None, timeout=1.0):
+    address, port = 'localhost', 3031  # TODO put this somewhere sane
+    def request(path, args=None):
+        headers = {'Content-Type': 'application/json;charset=utf-8'}
+        body = json.dumps(args)
+        try:
+            conn = http.client.HTTPConnection(address, port, timeout=30)
+            conn.request('GET', path, body=body, headers=headers)
+            response = conn.getresponse()
+            if response.status != http.client.OK:
+                raise Exception('server returned {}'.format(response.status))
+            reply = json.loads(response.read().decode('utf-8'))
+            return reply
+        finally:
+            conn.close()
     return request('/run', {'code': code, 'inputs': inputs, 'timeout': timeout})
 
+# Start and return a new Python interpreter process.
+def create():
+    directory = os.path.dirname(os.path.realpath(__file__))
+    script = os.path.join(directory, 'runner', 'interpreter.py')
+    p = subprocess.Popen([script],
+            stdin=subprocess.PIPE,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT)
+    # Set the non-blocking flag for stdout.
+    flags = fcntl(p.stdout, F_GETFL)
+    fcntl(p.stdout, F_SETFL, flags | os.O_NONBLOCK)
+    return p
+
+# Read any available bytes from the interpreter's stdout.
+def pull(interpreter):
+    stdout = interpreter.stdout.read()
+    if stdout:
+        stdout = stdout.decode('utf-8')
+    return stdout
+
+# Push a string to the interpreter's stdin.
+def push(interpreter, stdin):
+    interpreter.stdin.write(stdin.encode('utf-8'))
+    interpreter.stdin.flush()
+
+# Kill an interpreter process.
+def destroy(interpreter):
+    interpreter.kill()
+
 
 # Basic sanity check.
 if __name__ == '__main__':
diff --git a/python/runner/interpreter.py b/python/runner/interpreter.py
new file mode 100755
index 0000000..5fa320a
--- /dev/null
+++ b/python/runner/interpreter.py
@@ -0,0 +1,8 @@
+#!/usr/bin/python3
+
+# Apparently there is no (working) way to get a non-blocking stdout if we call
+# the Python interpreter directly with subprocess.Popen. For some reason, this
+# works.
+
+import code
+code.interact(banner='')